When running as main, handle leading python

[akamgm]

Previously, calling the parser directly on a file with leading python would break, eg:

$python aipl/parser.py examples/hanukkah-of-data-5783.aipl
Parsing:  examples/hanukkah-of-data-5783.aipl
Traceback (most recent call last):
...
lark.exceptions.UnexpectedCharacters: No terminal matches '@' in the current parser context, at line 1 col 1

@defop('sql', 0, 1.5)
^
Expected one of: 
        * _EMPTY_LINE
        * __ANON_0

Prepending an explicit !!python\n to the input, as AIPL.run() does, handles it correctly.

[anjakefala]

I really appreciate you addressing this!

[akamgm]

Happy to! Although I think there's a better long-term fix - see this issue.